/*
    This file is part of the iText (R) project.
    Copyright (c) 1998-2022 iText Group NV
    Authors: iText Software.

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU Affero General Public License version 3
    as published by the Free Software Foundation with the addition of the
    following permission added to Section 15 as permitted in Section 7(a):
    FOR ANY PART OF THE COVERED WORK IN WHICH THE COPYRIGHT IS OWNED BY
    ITEXT GROUP. ITEXT GROUP DISCLAIMS THE WARRANTY OF NON INFRINGEMENT
    OF THIRD PARTY RIGHTS
    
    This program is distributed in the hope that it will be useful, but
    WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
    or FITNESS FOR A PARTICULAR PURPOSE.
    See the GNU Affero General Public License for more details.
    You should have received a copy of the GNU Affero General Public License
    along with this program; if not, see http://www.gnu.org/licenses or write to
    the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
    Boston, MA, 02110-1301 USA, or download the license from the following URL:
    http://itextpdf.com/terms-of-use/
    
    The interactive user interfaces in modified source and object code versions
    of this program must display Appropriate Legal Notices, as required under
    Section 5 of the GNU Affero General Public License.
    
    In accordance with Section 7(b) of the GNU Affero General Public License,
    a covered work must retain the producer line in every PDF that is created
    or manipulated using iText.
    
    You can be released from the requirements of the license by purchasing
    a commercial license. Buying such a license is mandatory as soon as you
    develop commercial activities involving the iText software without
    disclosing the source code of your own applications.
    These activities include: offering paid services to customers as an ASP,
    serving PDFs on the fly in a web application, shipping iText with a closed
    source product.
    
    For more information, please contact iText Software Corp. at this
    address: sales@itextpdf.com
 */
using System;
using System.Collections.Generic;
using System.IO;
using iTextSharp.text.pdf.codec;
using iTextSharp.text.exceptions;
using iTextSharp.text.error_messages;
using System.util.collections;

namespace iTextSharp.text.pdf {


    /**
     * Encapsulates filter behavior for PDF streams.  Classes generally interace with this
     * using the static GetDefaultFilterHandlers() method, then obtain the desired {@link IFilterHandler}
     * via a lookup.
     * @since 5.0.4
     */
    // Dev note:  we eventually want to refactor PdfReader so all of the existing filter functionality is moved into this class
    // it may also be better to split the sub-classes out into a separate package
    public sealed class FilterHandlers {
        /**
         * The main interface for creating a new {@link IFilterHandler}
         */
        public interface IFilterHandler {
            byte[] Decode(byte[] b, PdfName filterName, PdfObject decodeParams, PdfDictionary streamDictionary);
        }

        /** The default {@link IFilterHandler}s used by iText */
        private static IDictionary<PdfName, IFilterHandler> defaults;

        static FilterHandlers() {
            Dictionary<PdfName, IFilterHandler> map = new Dictionary<PdfName, IFilterHandler>();

            map[PdfName.FLATEDECODE] = new Filter_FLATEDECODE();
            map[PdfName.FL] = new Filter_FLATEDECODE();
            map[PdfName.ASCIIHEXDECODE] = new Filter_ASCIIHEXDECODE();
            map[PdfName.AHX] = new Filter_ASCIIHEXDECODE();
            map[PdfName.ASCII85DECODE] = new Filter_ASCII85DECODE();
            map[PdfName.A85] = new Filter_ASCII85DECODE();
            map[PdfName.LZWDECODE] = new Filter_LZWDECODE();
            map[PdfName.CCITTFAXDECODE] = new Filter_CCITTFAXDECODE();
            map[PdfName.CRYPT] = new Filter_DoNothing();
            map[PdfName.RUNLENGTHDECODE] = new Filter_RUNLENGTHDECODE();

            defaults = new ReadOnlyDictionary<PdfName, IFilterHandler>(map);
        }

        /**
         * @return the default {@link IFilterHandler}s used by iText
         */
        public static IDictionary<PdfName, IFilterHandler> GetDefaultFilterHandlers() {
            return defaults;
        }

        /**
        * Creates a {@link MemoryLimitsAwareOutputStream} which will be used for decompression of the passed pdf stream.
        *
        * @param streamDictionary the pdf stream which is going to be decompressed.
        * @return the {@link ByteArrayOutputStream} which will be used for decompression of the passed pdf stream
        */
        public static MemoryStream EnableMemoryLimitsAwareHandler(PdfDictionary streamDictionary) {
            MemoryLimitsAwareOutputStream outputStream = new MemoryLimitsAwareOutputStream();
            MemoryLimitsAwareHandler memoryLimitsAwareHandler = null;
            if (streamDictionary is PRStream && null != ((PRStream)streamDictionary).Reader) {
                memoryLimitsAwareHandler = ((PRStream)streamDictionary).Reader.GetMemoryLimitsAwareHandler();
            }
            else {
                // We do not reuse some static instance because one can process pdfs in different threads.
                memoryLimitsAwareHandler = new MemoryLimitsAwareHandler();
            }
            if (null != memoryLimitsAwareHandler && memoryLimitsAwareHandler.ConsiderCurrentPdfStream) {
                outputStream.SetMaxStreamSize(memoryLimitsAwareHandler.GetMaxSizeOfSingleDecompressedPdfStream());
            }
            return outputStream;
        }

        /**
         * Handles FLATEDECODE filter
         */
        private class Filter_FLATEDECODE : IFilterHandler {
            public byte[] Decode(byte[] b, PdfName filterName, PdfObject decodeParams, PdfDictionary streamDictionary) {
                MemoryStream outS = EnableMemoryLimitsAwareHandler(streamDictionary);
                b = PdfReader.FlateDecode(b, outS);
                b = PdfReader.DecodePredictor(b, decodeParams);
                return b;
            }
        }

        /**
         * Handles ASCIIHEXDECODE filter
         */
        private class Filter_ASCIIHEXDECODE : IFilterHandler {
            public byte[] Decode(byte[] b, PdfName filterName, PdfObject decodeParams, PdfDictionary streamDictionary) {
                MemoryStream outS = EnableMemoryLimitsAwareHandler(streamDictionary);
                b = PdfReader.ASCIIHexDecode(b, outS);
                return b;
            }
        }

        /**
         * Handles ASCIIHEXDECODE filter
         */
        private class Filter_ASCII85DECODE : IFilterHandler {
            public byte[] Decode(byte[] b, PdfName filterName, PdfObject decodeParams, PdfDictionary streamDictionary) {
                MemoryStream outS = EnableMemoryLimitsAwareHandler(streamDictionary);
                b = PdfReader.ASCII85Decode(b, outS);
                return b;
            }
        }

        /**
         * Handles LZWDECODE filter
         */
        private class Filter_LZWDECODE : IFilterHandler {
            public byte[] Decode(byte[] b, PdfName filterName, PdfObject decodeParams, PdfDictionary streamDictionary) {
                MemoryStream outS = EnableMemoryLimitsAwareHandler(streamDictionary);
                b = PdfReader.LZWDecode(b, outS);
                b = PdfReader.DecodePredictor(b, decodeParams);
                return b;
            }
        }

        /**
         * Handles CCITTFAXDECODE filter
         */
        private class Filter_CCITTFAXDECODE : IFilterHandler {
            public byte[] Decode(byte[] b, PdfName filterName, PdfObject decodeParams, PdfDictionary streamDictionary) {
                PdfNumber wn = (PdfNumber)PdfReader.GetPdfObjectRelease(streamDictionary.Get(PdfName.WIDTH));
                PdfNumber hn = (PdfNumber)PdfReader.GetPdfObjectRelease(streamDictionary.Get(PdfName.HEIGHT));
                if (wn == null || hn == null)
                    throw new UnsupportedPdfException(MessageLocalization.GetComposedMessage("filter.ccittfaxdecode.is.only.supported.for.images"));
                int width = wn.IntValue;
                int height = hn.IntValue;

                PdfDictionary param = decodeParams is PdfDictionary ? (PdfDictionary)decodeParams : null;
                int k = 0;
                bool blackIs1 = false;
                bool byteAlign = false;
                if (param != null) {
                    PdfNumber kn = param.GetAsNumber(PdfName.K);
                    if (kn != null)
                        k = kn.IntValue;
                    PdfBoolean bo = param.GetAsBoolean(PdfName.BLACKIS1);
                    if (bo != null)
                        blackIs1 = bo.BooleanValue;
                    bo = param.GetAsBoolean(PdfName.ENCODEDBYTEALIGN);
                    if (bo != null)
                        byteAlign = bo.BooleanValue;
                }
                byte[] outBuf = new byte[(width + 7) / 8 * height];
                TIFFFaxDecompressor decoder = new TIFFFaxDecompressor();
                if (k == 0 || k > 0) {
                    int tiffT4Options = k > 0 ? TIFFConstants.GROUP3OPT_2DENCODING : 0;
                    tiffT4Options |= byteAlign ? TIFFConstants.GROUP3OPT_FILLBITS : 0;
                    decoder.SetOptions(1, TIFFConstants.COMPRESSION_CCITTFAX3, tiffT4Options, 0);
                    decoder.DecodeRaw(outBuf, b, width, height);
                    if (decoder.fails > 0) {
                        byte[] outBuf2 = new byte[(width + 7) / 8 * height];
                        int oldFails = decoder.fails;
                        decoder.SetOptions(1, TIFFConstants.COMPRESSION_CCITTRLE, tiffT4Options, 0);
                        decoder.DecodeRaw(outBuf2, b, width, height);
                        if (decoder.fails < oldFails) {
                            outBuf = outBuf2;
                        }
                    }
                }
                else {
                    TIFFFaxDecoder deca = new TIFFFaxDecoder(1, width, height);
                    deca.DecodeT6(outBuf, b, 0, height, 0);
                }
                if (!blackIs1) {
                    int len = outBuf.Length;
                    for (int t = 0; t < len; ++t) {
                        outBuf[t] ^= 0xff;
                    }
                }
                b = outBuf;
                return b;
            }
        }

        /**
         * A filter that doesn't modify the stream at all
         */
        private class Filter_DoNothing : IFilterHandler {
            public byte[] Decode(byte[] b, PdfName filterName, PdfObject decodeParams, PdfDictionary streamDictionary) {
                return b;
            }
        }

        /**
         * Handles RUNLENGTHDECODE filter
         */
        private class Filter_RUNLENGTHDECODE : IFilterHandler {
            public byte[] Decode(byte[] b, PdfName filterName, PdfObject decodeParams, PdfDictionary streamDictionary) {
                // allocate the output buffer
                MemoryStream baos = EnableMemoryLimitsAwareHandler(streamDictionary);
                sbyte dupCount = -1;
                for (int i = 0; i < b.Length; i++) {
                    dupCount = (sbyte)b[i];
                    if (dupCount == -128) break; // this is implicit end of data

                    if (dupCount >= 0 && dupCount <= 127) {
                        int bytesToCopy = dupCount + 1;
                        baos.Write(b, i, bytesToCopy);
                        i += bytesToCopy;
                    }
                    else {
                        // make dupcount copies of the next byte
                        i++;
                        for (int j = 0; j < 1 - (int)(dupCount); j++) {
                            baos.WriteByte(b[i]);
                        }
                    }
                }
                return baos.ToArray();
            }
        }
    }
}
